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Diffstat (limited to 'examples/binary.py')
-rw-r--r-- | examples/binary.py | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/examples/binary.py b/examples/binary.py new file mode 100644 index 0000000..3b543e5 --- /dev/null +++ b/examples/binary.py @@ -0,0 +1,88 @@ +# binary.py - working with binary data +# +# Copyright (C) 2001-2004 Federico Di Gregorio <fog@debian.org> +# +# This program is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by the +# Free Software Foundation; either version 2, or (at your option) any later +# version. +# +# This program is distributed in the hope that it will be useful, but +# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY +# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License +# for more details. + +## put in DSN your DSN string + +DSN = 'dbname=test' + +## don't modify anything below tis line (except for experimenting) + +import sys, psycopg + +if len(sys.argv) > 1: + DSN = sys.argv[1] + +print "Opening connection using dns:", DSN +conn = psycopg.connect(DSN) +print "Encoding for this connection is", conn.encoding + +curs = conn.cursor() +try: + curs.execute("CREATE TABLE test_binary (id int4, name text, img bytea)") +except: + conn.rollback() + curs.execute("DROP TABLE test_binary") + curs.execute("CREATE TABLE test_binary (id int4, name text, img bytea)") +conn.commit() + +# first we try two inserts, one with an explicit Binary call and the other +# using a buffer on a file object. + +data1 = {'id':1, 'name':'somehackers.jpg', + 'img':psycopg.Binary(open('somehackers.jpg').read())} +data2 = {'id':2, 'name':'whereareyou.jpg', + 'img':buffer(open('whereareyou.jpg').read())} + +curs.execute("""INSERT INTO test_binary + VALUES (%(id)d, %(name)s, %(img)s)""", data1) +curs.execute("""INSERT INTO test_binary + VALUES (%(id)d, %(name)s, %(img)s)""", data2) + +# now we try to extract the images as simple text strings + +print "Extracting the images as strings..." +curs.execute("SELECT * FROM test_binary") + +for row in curs.fetchall(): + name, ext = row[1].split('.') + new_name = name + '_S.' + ext + print " writing %s to %s ..." % (name+'.'+ext, new_name), + open(new_name, 'wb').write(row[2]) + print "done" + print " python type of image data is", type(row[2]) + +# extract exactly the same data but using a binary cursor + +print "Extracting the images using a binary cursor:" + +curs.execute("""DECLARE zot CURSOR FOR + SELECT img, name FROM test_binary FOR READ ONLY""") +curs.execute("""FETCH ALL FROM zot""") + +for row in curs.fetchall(): + name, ext = row[1].split('.') + new_name = name + '_B.' + ext + print " writing %s to %s ..." % (name+'.'+ext, new_name), + open(new_name, 'wb').write(row[0]) + print "done" + print " python type of image data is", type(row[0]) + +# this rollback is requires because we can't drop a table with a binary cusor +# declared and still open +conn.rollback() + +curs.execute("DROP TABLE test_binary") +conn.commit() + +print "\nNow try to load the new images, to check it worked!" |